that small center shield is there to screen off the metal dome resonance above 20khz, above the hearing range. the frequency response looks better this way. drawback is that this shield also creates a cavity resonance between it and the dome and is more easily heard as the distortion goes up
Why do I care about the response curve above the hearing range? Are there harmonics below 20k or something. I wonder if this also makes the driver sound less harsh as metal domes have a tendency to do?
George
In order of preference:
SB26ADC-C000-4 well behaved aluminium tweeter (see Troel's site for test and amazing low distortion numbers)
SB29RDAC-C000-4 a ring radiator I like
SB26STAC-C000-4 can sound harsh if crossed over too low with the wrong slope
I also have a soft spot for the old SEAS 27TFFC which is so easy to work with and I still have a pair in use.
SB26ADC-C000-4 well behaved aluminium tweeter (see Troel's site for test and amazing low distortion numbers)
SB29RDAC-C000-4 a ring radiator I like
SB26STAC-C000-4 can sound harsh if crossed over too low with the wrong slope
I also have a soft spot for the old SEAS 27TFFC which is so easy to work with and I still have a pair in use.
I've heard all 3 of those SB (..though in different designs).
-when used properly I very much prefer the electrostatic-like clarity of the STAC. It's a picky tweeter though, both with respect to the crossover and the partnering midrange/mid-bass driver. It's not *that* difficult to work with, but it's not particularly easy to get an excellent result either.
The ADC is just an excellent tweeter all-round: smooth and not at all "edgy" like the STAC.. BUT it doesn't have the same clarity either, nor is dispersion as good. Just a LOT easier to implement into any given design though. With this tweeter, there really isn't much reason to look for any other dome tweeter (unless you are looking for something a bit "more" that it doesn't quite offer, and in many respects this tweeter does offer "more" - but does so in certain aspects that might not meet an ultimate objective).
The RDAC sounds clean but "constipated" (over-damped) to me - lacking depth in particular. It sounds like a good cheap tweeter OTHER than the fact it can extend a fair bit lower in freq. than other cheap tweeters. IF I were to look to a ring design with good extension, it would be from Scan Speak (or Peerless) - and it wouldn't be a double-ring design.
-when used properly I very much prefer the electrostatic-like clarity of the STAC. It's a picky tweeter though, both with respect to the crossover and the partnering midrange/mid-bass driver. It's not *that* difficult to work with, but it's not particularly easy to get an excellent result either.
The ADC is just an excellent tweeter all-round: smooth and not at all "edgy" like the STAC.. BUT it doesn't have the same clarity either, nor is dispersion as good. Just a LOT easier to implement into any given design though. With this tweeter, there really isn't much reason to look for any other dome tweeter (unless you are looking for something a bit "more" that it doesn't quite offer, and in many respects this tweeter does offer "more" - but does so in certain aspects that might not meet an ultimate objective).
The RDAC sounds clean but "constipated" (over-damped) to me - lacking depth in particular. It sounds like a good cheap tweeter OTHER than the fact it can extend a fair bit lower in freq. than other cheap tweeters. IF I were to look to a ring design with good extension, it would be from Scan Speak (or Peerless) - and it wouldn't be a double-ring design.
Ading waveguides is mentioned here; do any of you know where one can download files(stl?) for a 3d printer. I would like to print a 5-6 inch waveguide for my 28mm (nominal -I measure it as 26mm) dometweeter
Brandons waveguides are very good. I am currently enjoying my ScanSpeak R2604 with just 2 component crossover, 4,7uF cap and 1,5Ohm resistor.
If I was doing a waveguide tweeter, this is the one I'd use:
https://www.scan-speak.dk/datasheet/pdf/d2604-833000.pdf
-it's a "ring" + dome, rather than a double ring like the XTs or the SB RDAC-types.
If you have to go cheaper, and don't need the excursion at all, then the Peerless variation is also good (maybe a bit better at higher freq.s and a bit worse at lower freq.s):
https://www.parts-express.com/pedocs/specs/264-1478--tymphany-dx25bg60-04-spec-sheet.pdf
https://www.scan-speak.dk/datasheet/pdf/d2604-833000.pdf
-it's a "ring" + dome, rather than a double ring like the XTs or the SB RDAC-types.
If you have to go cheaper, and don't need the excursion at all, then the Peerless variation is also good (maybe a bit better at higher freq.s and a bit worse at lower freq.s):
https://www.parts-express.com/pedocs/specs/264-1478--tymphany-dx25bg60-04-spec-sheet.pdf
The DX version I have heard in a waveguide with an Fc of 1kHz, and it took all the amplifier could give it. The face is cast aluminum, not plastic, and the Xmax is measured to be small; but that is mechanical measurement and not linear stroke. They are very capable tweeters.
Later,
Wolf
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